What verse tells us to confess our sins to receive forgiveness?

I believe the passage in question is 1 John 1:9: “If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.” KJV

One must remember this promise is given to Christians, that is, those who have already obeyed the Gospel. This promise is not for someone who is outside of Christ (a non-Christian). No alien sinner (a non-Christian) was ever told to confess his sins to God in order to be saved. None was ever told to accept Christ as their personal savior and pray the sinner’s prayer. All were instructed in the way of obedience.

For the non-Christian to receive forgiveness of sins, one must:

Hear and Believe the word of God — Romans 10:17

Believe in the Christ, including His perfect life, death for our sins, and resurrection from the dead – John 8:24; 1 Corinthians 15:1-4

As we strive to live faithfully (also called “walking in the light” – 1 John 1:7), we will sin. However, we do not have to be baptized again every time we sin. God gives the Christian the privilege of repentance, prayer and confession of sins (e.g. Acts 8:5-34, esp. beginning in verse 24).